RE:MilkShake anyone?

["John Fielding" <johnf@domain.elided>]

The cylinder liner bottom O rings seals are pretty tough to replace with the motor in the
car.  First off the liners suffer from severe fretting corrosion into the ali block and
usually need to be driven out from the bottom.  That means the crankshaft has to come out.
The crankshaft cannot be removed with the block in the vehicle!  Try it, you will see what
I mean.

I have found serious corrosion on several Alfa motors where the liners fit into the block.
Also the tiny O rings perish with time and cause the liners to regress further into the
block.  This causes two things.  First off the liners piddle water into the sump and the
head gasket clamping pressure is reduced and soon head gasket problems occur.  Either way
it is an engine out exercise and do the job properly.

Mu Alfa-guru mechanic recommends that when the liners & O rings are replaced that the O
rings are backed up with some paper gaskets to increase the clamping pressure and to smear
some high temperature RTV gasket paste on the joints to help stop leaks in future.  I know
this isn't mentioned in the "official manuals" but something he has learnt with over 25
years of working on Alfa motors.  The corrosion causing the liners to regress can be quite
severe.  On one motor I measured about 0.75mm.  The reason?  The motor did not have
antifreeze! Many people here in sub-saharan Africa thinks anti-freeze is unnecessary.
Also the thin chamfered lip in the block gets corroded away and the O ring then has
nowhere to seat.  BTW Did I mention that he was the person who designed the factory turbo
conversion for Alfa here?  This "basket case" motor needed an appropriate amount machined
off the block top face to make it usable!


It is especially important to check the liner protrusion when first installed to ensure
there will be sufficient clamping pressure between the cylinder head/gasket/liners.  More
is better than less, up to about 0.3mm being preferable if you are running a high
compression ratio above 10:1.  The "crush" of the metal rings in the head gasket can
tolerate a lot more than the normal protrusion allows.  Some of the racers here have the
head "ringed" to insert a thin copper wire to improve sealing.  I have also seen the same
done to the liner tops.  One drag racer I know runs a highly modified 2L motor with 14:1
CR and he has not only a ringed head and liners but also a solid copper head gasket.  This
motor has twin turbos and a nitrous "squeeze" and has now run reliably for more than two
years.

I am puzzled why the motor does not suffer from overheating.  Either the thermostat is
removed or the gauge is telling lies?

John
Durban
South Africa
Alfetta 1.8L turbo
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